Various types of clinical analyzers for the automated analysis of samples such as blood, serum, urine and plasma are in practical use. Since there is a strong demand for offering a wide variety of analytical functions and with a view to improve effectiveness in sample processing, modern analyzers usually process samples in parallel and/or split individual samples into a number of aliquots for simultaneous processing. As a result, modern analyzers are subject to a number of pipetting operations. Otherwise, analysis typically requires the samples to be combined with one or more reagents by use of pipettes to initiate chemical or immunochemical reactions with respect to specific substances contained therein. Some reagents such as suspensions of magnetic beads need to be homogenized before use which most typically is done with stirrers having paddles on their free ends which are lowered into the reagents.
It has been found advantageous to employ reusable pipettes and stirrers which compared to disposables reduce the costs of sample processing. Thorough washing of the outside surfaces of such reusables is however required in-between consecutive operations to avoid carry-over and cross-contamination.
Washing devices for washing the outer surfaces of pipettes and stirrers are known from the prior art. It is common practice to insert these objects into a cavity filled with washing fluid which, however, does not always yield the desired result. The washing fluid has to be replaced after one or more washing steps resulting in a lot of waste fluid. A more sophisticated washing device is described in U.S. Pat. No. 7,300,525 B2. This washing device comprises a cavity for holding a washing fluid provided with a fluid duct for filling or emptying the cavity. Furthermore, one or more nozzles are directed towards the interior of the cavity to dispense washing fluid directly onto the pipettes. Another approach is described in U.S. Pat. No. 4,730,631, in which both the inside and outside surfaces of pipettes are washed by lowering the pipettes into a receptacle and forcibly dispensing washing fluid therethrough to fill the receptacle with washing fluid.